


The Knife’s Edge

by Anonymous



Category: Supernatural
Genre: Alternate Universe- No Supernatural, Bondage, Bottom Castiel (Supernatural), Bottom Castiel/Top Sam Winchester, Breathplay, Castiel Loves Sam Winchester, Dangerous Relationship, Dark Sam Winchester, FBI Agent Castiel, M/M, Rough Sex, Sam Is Obsessed With Castiel, Serial Killer Sam Winchester, Unhealthy Relationships
Language: English
Status: Completed
Published: 2018-12-08
Updated: 2018-12-08
Packaged: 2019-09-14 03:26:34
Rating: Mature
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 776
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16905222
Author URL: https://archiveofourown.org/
Summary: Sam doesn’t understand any of it.This thing he has with Cas, it’s like the FBI agent is balancing on a knife’s edge.  Except Cas isn’t afraid of falling.Or of putting his life in Sam’s hands.





	The Knife’s Edge

Sometimes, he has to wait. 

Occasionally, it’s by choice: an attempt to control himself, to reign in his compulsion before it owns him completely and he becomes some feral, out of control thing that will be easy to snare and kill.

More often, it’s by necessity; things have to settle. He has to bide his time until some high profile politician is caught in a seedy scam, or a pop group breaks up, or there’s a disaster somewhere to trend and occupy all the front pages and top stories on CNN and the rest.

And then there’s when he receives a warning from his own personal guardian angel that they’re closing in on him, to run.

That’s why, when he hears the ringtone from his pocket - the thunderous opening to _Dies Irae_ \- and it cuts off seconds later, Sam keeps walking past the motel where he’s shacked up, away from the car he stole, and jumps on the first bus that passes.

There’s nothing he’s leaving in that room that he can’t pick up again someplace else. Nothing there they’ll find to help catch him. 

He’ll never be taken by them. Never.

++

It’s not something Sam pretends to understand.

Castiel groans beneath him, warm and tight and helpless as Sam plays with his body, the handcuffs clinking as he writhes and struggles and begs.

None of it makes sense. That this man who should be hunting him, who should be taking him at gunpoint has instead left himself so frighteningly vulnerable.

Sam could end him. He could take that pillow and hold it down over his face and feel the fight drain out of Cas.

He could sneak that knife he has on the floor, hidden beneath his jeans, up and quickly slit his throat, let the spray of blood decorate both of them.

He could take Cas and leave him in that abandoned house he has as a bolt hole. It’s miles from anywhere, and there’s a curved piece of rebar in the basement that Sam set in concrete there himself.

He could cuff Cas to it, and walk away, never go back, knowing it would take three days or so for Cas to die slowly, painfully, alone and in the dark.

He’s thought of so many ways he could do it. That he wants to do it.

But he never does.

And he won’t. Cas seems to know it, too.

Which is why he just looks up at Sam, eyes wide and full of lust instead of fear when Sam puts his hand around Cas’s neck and squeezes. 

He thrusts into him harder, then, painful and rough, and Cas arches up to meet each one, and the bruising grip around his throat.

And then he’s coming, pulsing over himself, and Sam keeps squeezing that tanned throat until he is too.

He lets go, slaps Cas’s cheek a few times to bring him around, makes sure he’s breathing normally again.

He unlocks the cuffs, and dumps them back on top of the sharp suit decorating the floor.

Glances at the shoulder holster and sidearm. Adds another fantasy to the catalogue, waiting until Cas is getting dressed before he shoots him in the head with his own gun.

Cas sits up, rubbing at his throat, body wearing Sam’s scratches and bite marks, and reddened skin that will surely bruise in colourful shades over the days to come.

Sam never gets to see those though; there’s too long between these encounters, and by then all he’s done to Cas has healed.

On the outside, anyway. Because just as Sam knows he’s sick, and what he does is wrong, he knows Cas’s love for him is just as much the sign of another damaged soul.

“You should go,” he says, and he knows Cas can tell very well what he means.

Cas climbs into his lap, still naked, and kisses him.

Sam doesn’t resist. He can’t.

There is just one person in this entire world who loves him, and Sam frequently has dreams about new ways of killing him.

“You’ll never hurt me.”

“You don’t know that.”

“I know it, Sam. I can’t live without you.”

“If they catch you…”

Cas huffs. This is a conversation they’ve had before, the risks Cas takes by warning him when the FBI task force he’s part of starts to close in on Sam. “They won’t.”

He’s right. They won’t, because Sam has a plan for that too. If they ever try to take Cas, if it seems they’re ever getting too close, Sam will find a way to kill him first.

And then he’ll kill himself.

They’re both damned either way.


End file.
